The Halloween trick that conjures ghosts of the mind

AS I prepare the room, it feels as if I'm getting ready for a seance. I close the curtains to block out most of the light and place two chairs about a metre apart. I prop up a large mirror on one and sit in the other so that I can just see my reflection in the near darkness. Then I set a timer for 10 minutes and wait patiently for the faces to appear.

When they do, it is startling. At first the distortions in the mirror are small: a lifted eyebrow, a twitch of the mouth. But after seven minutes my reflection suddenly looks fake, like a waxwork. And then it is no longer my face. For a few seconds an old man with a thickly wrinkled brow and down-turned mouth stares back at me.